Grave concern

[aljay]

I had a high risk exposure with a prostitute in the uk 10 days ago. The condom slipped and was fully exposed. After receiving oral the head of my penis was sore which has raised more anxiety as I think this may have made me more susceptible. I had a HIV duo test with P24 antigen at day 9. I have read that the P24 antigen is produced in excess following immediate infection and is detectable approx 7-21 days after infection. This test came back negative. Is this reassuring please help me. I am aware that an antibody test at 3 months is conclusive but have read several medical journals that say p24 antigen is produced if infected by hiv-1 or hiv-2 in the early stages of infection, i.e. after 7 days. Is this true? I intend on getting tested again at 28 days but just wanted to know how reassuring this p24 antigen test result is in terms of percentage accuracy. Many Thanks.

[Edward W Hook, MD]

Many many scienticfic studies.  This is a concensus figure.  EWH

[aljay]

Hi Doctor,

I am just wondering where you state that even if a woman was hiv + the chance of transmission to a male in unprotected vaginal is 1/2000. On what basis do you say this?

[Edward W Hook, MD]

Yes, you are correct, the p24 should pick up HIV-1 or HIV-2, even though the chances of your getting HIV-2 are near zero.

there are not good data on just how often the p24 would or would not pick up infection.  As I said before, what your p24 results do is to ADD confidence to the fact that your exposure is NO RISK.  

Now, please no further anxiety-driven questions.  This was a no risk event

EWH

[aljay]

Thanks this is reassuring. Just to clarify is it the case that p24 antigen would be produced if one was infected with the hiv1 and hiv 2 virus or is it just applicable to one of the strains?

Hopefully i'm not asking too much but how reliable (approx %age terms) is the p24 reliable at day8/9?

Thanks again.

[Edward W Hook, MD]

I have reviewed your questions to the HIV prevention community and can see that you are quite concerned about the exposure you had.  I will try to reinforce what they have already told you.  You risk is very low.  You did not need PEP (it is good that you were denied) and your chances of having HIV are vanishingly low.  To provide more detail:

1.  Even though she was a CSW, the chances that she had HIV are very low.  Most CSWs do not have HIV.
2.  The condom provided partial protection and the exposure was brief.
3.  Even if she had HIV, your chance of infection from a single exposure to an HIIV infected partner is less than 1 inf3ection in 1000 exposures, even if the head of your penis was irritated.
4.  the P24, while not perfect, is additional strong indication that you do not have HIV.

You  have nothing to worry about.  Get the follow-up antibody test as planned
EWH